Abrasive articles and method of making abrasive articles



Nov. 29, 1966 W4 ABERNATHY 3,287,861

ABRASIVE ARTICLES AND METHOD OF MAKING ABRASIVE ARTICLES Filed March 6, 1964 William J.l-\bernaihy,

INVENTOR.

fw ATTORNEY.

United States Patent 3,287,861 ABRASIVE ARTICLES AND METHOD 3 F MAKEJG ABRASIVE ARTICLES Villiarn J. Abernathy, Huntsville, Ala., assignor to Thiokoi Chemical Corporation, Bristol, Pa, :1 corporation of Delaware Filed Mar. 6, 1964, Ser. No. 350,084 11 Claims. (Cl. 51-204) This invention relates to the general field of abrasive machining and particularly to lapping plates, abrasive surfaced articles and methods for making the same.

In one area of abrasive machining, which is termed lapping, the goal is to produce smooth and accurate surfaces. The abrasive supporting member used in such work is termed a lap, lapping plate or lapping carrier, which terms shall be herein interchangeably. Lapping plates are usually made of fairly soft and porous materials such as cas't-i-ron, copper, brass, and lead. Some are made of granite. Lapping plates become abrasive articles or laps when they are combined with an abrasive which is charged or rolled into the surface of the plate. Examples of abrasives so combined are: emery fl'our, diamond dust, silicon carbide and aluminum oxide. Abrasive articles as contemplated herein, of the lapping variety and of the type used in more coarse work, may take an unlimited number of configurations, depending only upon the contour of the article to be machined.

The-re are two major faults with the abrasive articles described above insofar as they are lapping devices. First, a lapping device is only useful so long as it retains its contour to a very precise degree, within a few microinches, and experience indicates that with the known types of lapping devices referred to above useful life, before refinish-ing is necessary, is often quite short. Second, galling or scratching of articles being lapped is a common occurrence.

Another approach to the construction of abrasive laps, apparently employed to .a very limited extent and for special uses, is to bond the abrasive to the lapping plate or supporting structure. This same approach is widely applied to less precision abrasive machining devices such as abrasive w eels for grinding. The difficulty, of course, is to find a bonding agent that will hold the abrasive grits in place. Particularly is this so where severe temperature and pressure conditions are experienced. In an etfort to find a bonding agent equal to the job many types have been employed and they include; silicate, vitrified, shellac, rubber, resinoid, and certain metal bondings. None have been found which provide a factor of durability approaching that of the extremely hard abrasives, such as diamond, which they must hold in place. In other words the bonding or holding agent is the weak link in the structure. This is also true with respect to the more conventional abrasive holding agents, the lapping plates described in the preceding paragraph wherein wear and galling are the difiiciencies.

It is the object of this invention to overcome the aforesaid difficulties and to provide a basic advance in the art of abrasive machining.

The attached drawing forming a part of this specification is a pictorial View, partly in section, of an embodiment of this invention.

In accordance with the invention an abrasive supporting member is cut or formed of an anodizable stock material such as aluminum. The wor-king surface or surfaces are then machined or finished to the degree of finish determined by the requirements for use of the end product. Where the use is to be lapping and thus the end product a lapping plate the working surfaces are lapped at a 4 to 6 micro-inch finish. For extreme precision work 3,2818% Patented Nov. 29, I966 the stock material is then stress relieved in accordance with standard techniques which comprise first elevating the temperature of the material substantially above room temperature and then lowering it substantially below room temperature. After this, the surfaces are relapped to the prior 4 to 6 micro-inch finish. At this point, in accordance with one aspect of the invention, the material is subjected to anodizing to form a hard anodic coating on working surfaces of at least .001 of an inch followed by relapping to the desired precision of contour which is at least to the precision of contour which existed prior to the anodizing step. Thus, an abrasive supporting member or lap is constructed. As such it may also be used as an accurate surface plate or gage block (erg. anodized metal veneer on normal steel gage block) and as a deburring or burnishing tool with either a smooth or serrated surface.

An a-basive article or tool for lapping is formed in accordance with a second aspect of the invention when the supporting member as described above is combined with an abrasive which is charged or rolled into the working surfaces of the supporting member. It has been discovered that despite the hardness of the anodic coating which now forms these surfaces, a factor which in accordance with prior teachings and practices would eliminate it from consideration as a lap, it has been found that this coating provides an ideal surface for holding a charge of abrasive grits. This is believed due to its porous characteristic which appears to firmly fix or wedgein the abrasive grit, and uniformly so. Tests have indicated a durability for laps made in the manner not possible with conventional laps and with an amazing freedom from galling In accordance with still another aspect of the invention an abrasive article or tool is constructed as shown in the drawing by combining the abrasive grits 1i] and aluminum supporting member 12 in the manner described just prior to the anodizing step. In these instances instead of the grits 10 of the rolled in abrasive being mechanically held as in the previous case they are held by the anodic coating 14 to a degree of bonding believed never to have been previously achieved. :For maximum cutting efficiency the surfaces 16 prepared in this manner D should be polished or otherwise treated to recess the anodic coating slightly with respect to the abrasive grits. One method is to buff or polish it using felt and an abrasive grit wherein the grit size is smaller than that originally charged into the surfaces prior to anodizing.

As is perhaps clear the anodic bonding technique is equally applicable to the construction of fine cutting devices such as abrasive laps and to the construction of coarse cutting devices such as abrasive saws, grinding wheels and the like. Abrasive grit size is chosen in terms of the character of the abrasive cut desired. Within the normal range of diamond abrasive grits employed, anodic bonding is believed to be the most effective bonding discovered for holding such abrasive grits, and vastly superior to the techniques cited above.

It is, of course, to be understood that in the construction of coarse accuracy devices that the steps outlined above relating to precision working of the anodizable material, where a lapping device was the end product, may be omitted.

With respect to all of the forms of articles constructed in accordance with the methods set forth above it can be clearly stated that new standards of performance and durability have been achieved. In view of the harder surfaces and abrasive holding and bonding characteristics provided, greater pressures and thus cutting speeds can be obtained. Galling of work due to scoring of lapping plates has been essentially eliminated and they are much easier to clean than conventional plates. Further, light metals, such as aluminum are used for abrasive tools rather than heavier materials such as cast iron, a distinct advantage in many instances.

Other uses of my invention will no doubt be appreciated by those skilled in the art and accordingly I do not wish to be limited except by the scope of the accompanying claims.

I claim:

1.The method of making an abrasive article comprising:

(A) Preparing from anodizable stock material a surface conforming to a desired contour;

(B) Next, substantially filling the pores of said surface with an abrasive grit; and

(C) Finally, anodizing said surface to at least an anodic coating thickness of 0.001 inch.

2. The method set forth in claim 1, wherein said abrasive grit is a harder material than said anodic coating.

3. The method set forth in claim 2, and including the further and subsequent step of lapping said surface while employing a second abrasive grit, said second abrasive grit being of smaller dimension particles than said first named abrasive grit.

4. The method set forth in claim 3, wherein said anodizable stock material is aluminum.

5. The method of making an abrasive article compris- (A) Charging a surface of an anodizable metal with an abrasive grit having a hardness greater than aluminum oxide;

(B) Anodizing the surface as charged in step A to provide with the anodic coating thus formed a bonding agent between particles of said abrasive grit.

6. The method set forth in claim 5, and including the further and subsequent step of recessing the limit of the 4. bonding agent below the general surface level of the abrasive grit.

7. The method set forth in claim 6, in which recessing is accomplished by abrasive machining with a grit particle size smaller than initially charged into the surface in step (A).

8. The method set forth in claim 7, wherein the abrasive grit employed in step (A) is diamond.

9. An abrasive article comprising:

(A) A supporting base comprising a material capable of being anodized;

(B) An anodized porous coating on a surface of said base;

(C) A plurality of abrasive grits positioned to form an abrasive surface conforming to said surface of said base; and A (D) Said abrasive grits being bonded in pores of said porous coating by said porous coating but protruding above the outer surface of said porous coating.

10. An abrasive article'as set forth in claim 9, wherein said base is aluminum.

11. An abrasive article as set forth in claim 10, wherein said abrasive grits are of diamond.

References Cited by the Examiner UNITED STATES PATENTS 2,585,128 2/1952 Howe et a1 20438.1 X 2,798,037 7/1957 Robinson 20458 X FOREIGN PATENTS 656,566 2/1938 Germany.

ROBERT C. RIORDON, Primary Examiner.

L. s. SELMAN, Assistant Examiner. 

9. AN ABRASIVE ARTICLE COMPRISING: (A) A SUPPORTING BASE COMPRISING A MATERIAL CAPABLE OF BEING ANODIZE; (B) AN ANODIZED POROUS COATING ON A SURFACE OF SAID BASE; (C) A PLURALITY OF ABRASIVE GRITS POSITIONED TO FORM AN AGRASIVE SURFACE CONFORMING TO SAID SURFACE OF SAID BASE; AND (D) SAID ABRASIVE GRITS BEING BONDED IN PORES OF SAID POROUS COATING BY SAID POROUS COATING BUT PROTRUDING ABOVE THE OUTER SURFACE OF SAID POROUS COATING. 